As we can see from its name NON-AMPED MODULE, AM0 has no amplification function. It has only one USB port, but no headphone port.
Therefore, AM0 is for users who like to use X7 as audio source while connecting to external DAC or AMP.
However, apart from the above difference, the AM0 can be used in the same way as other amp modules, such as charging, connecting to PC for USB DAC/ storage function or docking to K5/DK1.